1. Field of the Invention
The present invention relates to an intermediate transfer body and an image forming apparatus.
2. Description of the Related Art
In an electrophotographic image forming apparatus is employed a method in which a toner image is obtained by developing an electrostatic latent image on an electrostatic latent image bearing member with a toner and the toner image is transferred to a recording medium to form the toner image on the recording medium is used in an electrophotographic image forming apparatus. As a transfer method in an image forming apparatus is used a method in which a toner image formed on an electrostatic latent image bearing member is transferred to an intermediate transfer belt which bears and conveys a toner image transferred thereto, the toner image transferred to the intermediate transfer belt is electrostatically moved to a recording medium by a transfer section which faces the intermediate transfer belt with the recording medium interposed therebetween. A belt cleaning apparatus is arranged to remove a residual toner remaining on an outer peripheral surface of an intermediate transfer belt after transferring a toner image to a recording medium.
A blade type belt cleaning apparatus is widely used as a belt cleaning apparatus. The blade type belt cleaning apparatus is a belt cleaning apparatus in which a plate-like cleaning blade abuts on a surface which bears a toner image of an intermediate transfer belt and a residual toner remaining on an outer peripheral surface of the intermediate transfer belt is scraped off. In such a blade type belt cleaning apparatus, in the case where surface roughness of an outer peripheral surface of the intermediate transfer belt is large, an abutting portion of the cleaning blade catches on the outer peripheral surface of the intermediate transfer belt. As a result, the cleaning blade itself is damaged, and reversal phenomenon that the cleaning blade rides up due to rotation of the intermediate transfer belt occurs. Those problems decrease removal efficiency of the residual toner. The reversal phenomenon that the cleaning blade rides up markedly occurs at a portion corresponding to an end in a width direction of the intermediate transfer belt among abutting portions of the cleaning blade to the intermediate transfer belt.
To overcome those problems, Japanese Unexamined Patent Publication JP-A 11-95567 (1999) discloses an image forming apparatus in which a cleaning blade provided so as to be parallel to a width direction of an intermediate transfer belt abuts on an intermediate transfer belt having formed thereon difference in level extending in a width direction and having large surface roughness, and the intermediate transfer belt is rotated in a direction that friction coefficient to the abutting portion of the cleaning blade becomes smaller.
In recent years, an intermediate transfer belt comprising a base material made of polyimide, and an elastic layer formed on a surface of the base material is being used in an electrophotographic image forming apparatus in order to improve a toner image bearing ability of an intermediate transfer belt and transferability of a toner image to a recording medium.
In the case where the intermediate transfer belt having an elastic layer is applied to the image forming apparatus disclosed in JP-A 11-95567, the cleaning blade abuts on the elastic layer on an outer peripheral surface of the intermediate transfer belt.
The image forming apparatus disclosed in JP-A 11-95567 is constituted such that the intermediate transfer belt is rotated in a direction that friction coefficient to an abutting portion of the cleaning blade is decreased, Therefore, the cleaning blade abuts on the intermediate transfer belt such that a region having high difference in level and a region having low difference in level, formed on the outer peripheral surface of the intermediate transfer belt are repeated in this order, and removes a residual toner.
For this reason, when an abutting position of the cleaning blade to the outer peripheral surface of the intermediate transfer belt changes from the region having high difference in level to the region having low difference in level, the cleaning blade bounds on the outer peripheral surface of the intermediate transfer belt. As a result, not only the residual toner scraped off from the intermediate transfer belt may scatter, but the abutting portion of the cleaning blade may bite in the inside in a thickness direction from the outer peripheral surface of the intermediate transfer belt. The elastic layer on the outer peripheral surface of the intermediate transfer belt is a layer liable to undergo elastic deformation. Therefore, the abutting portion of the cleaning blade, particularly an end in a width direction of the cleaning blade, excessively bites in the inside in a thickness direction from the outer peripheral surface of the intermediate transfer belt. Thus, where the abutting portion of the cleaning blade bites in the outer peripheral surface of the intermediate transfer belt, reversal phenomenon of the cleaning blade occurs, and removal efficiency of a residual toner is decreased. Furthermore, in the case where the cleaning blade bounds on the outer peripheral surface of the intermediate transfer belt due to rotation of the intermediate transfer belt, the cleaning blade does not abut on a boundary portion between the region having high difference in level and the region having low difference in level on the outer peripheral surface of the intermediate transfer belt. As a result, a residual toner remaining on the boundary portion cannot be removed, and uniform cleaning performance to the outer peripheral surface of the intermediate transfer belt cannot be obtained.